- C diff testing
- FENa in AKI
- How to work up an elevated aPTT
- Which coag tests for oral anticoagulants?
- IVC diameter on US to evaluate intravascular volume status
C DIFF PCR – DO ALL POSITIVES NEED TREATMENT?
- Case: woman treated with full course metronidazole with diarrhea. Repeat C diff PCR is positive. WBC normal.
- Available tests: culture, ELISA for glutamate dehydrogenase, ELISA for toxin A or B, cytotoxic assay for cultured C diff, PCR.
- IDSA testing recommendations (2010)
- only test on loose stool
- stool culture most sensitive
- testing toxogenic culture is most specific
- ELISA suboptimal
- glutamate dehydrogenase screen followed by cytotoxic assay recommended by IDSA
- PCR is rapid, sensitive and specific (but more data needed)
- C diff rates skyrocketed in 2012 when PCR testing became widely available – but was this CLINICAL C diff? No.
- Polage CR, et al. Overdiagnosis of C diff Infection in the Molecular Test Era (2016)
- EIA toxin negative patients behave clinically the same regardless of whether they are PCR + or -.
- Conclusion: Treat the patient, not the PCR. If you’re concerned that the PCR is false pos, get the EIA toxin assay.
FRACTIONAL EXCRETION OF SODIUM: SHOULD I GIVE MY PATIENT IVF WITH A FENA < 1?
- Outpatient: prerenal causes 70%. Inpatient: 35-40%.
- Routinely throwing IVF at people worsens outcomes, so don’t do it.
- FENa tells us: what are our renal tubules doing with Na?
- But any drug that affects the renal tubules will screw up your FENa.
- Low FENa (< 1%) : 90% intravascular depletion, but…10% include oliguric pts with ATN, contrast-induced nephropathy, pigment nephropathy, obstructive nephropathy, low effective circulating volume, non-oliguric renal parenchymal injury
- FENa > 2%: 90% ATN. But 10% of prerenal patients, normal renal function with high NaCl intake, volume depleted patient with CRF, volume depletion with Na-altering meds, vomiting or NGT suctioning (to spill HCO3 you’ll spill Na with it).
- FEUrea: 35% on the way down with oliguria
- Well-hydrated pt’s have FEUrea 45-50%
- Have to have a normal GFR at baseline, AKI, oliguria, no Na-altering meds, and no mimickers – OK to use FENa.
ELEVATED aPTT AND POSITIVE ANTICARDIOLIPIN ANTIBODIES – TO ANTICOAGULATE OR NOT?
- Causes of elevated aPTT: heparin use, delays in running specimen, clotting factor deficiency (vWF, 8, 9, 11, 12), clotting factor inhibitor (same), APLAb, elevated Hct.
- Should repeat the aPTT – do a 1:1 mixing study.
- What are the APLAb? Lupus anticoagulant studies (dilute RVV, dilute thromboplastin time, etc.), anti-B2-GLP1, anticardiolipin antibody.
- What about incidental positive APLAs?
- ACLAs in 6.5% blood donors, but none with thrombosis at 3 years
- Pregnant women often have ACLAs and Lupus Anticoag (18 and 12% respectively)
- Triple positive patients 25% risk of clot at 5 years – and ASA prophylaxis does not help.
- Now followed for 13 years – 2.3% risk per patient year.
HIGH INR IN A PATIENT ON DABIGATRAN – DOES IT MEAN THEY’LL BLEED?
- Case: Pt with ortho fx, last dabigatran dose 24 h ago, elevated INR – when okay to go to OR?
- Why would we ever want to monitor levels of the TSOAs (target-specific oral anticoagulants)?
- Urgent/emergency surgery
- Suspected hemorrhage
- Concern for overdose
- Acute thrombosis on therapy
- Concern for compliance
- Dabigatran: Ecarin clotting time or dilute thrombin time. In an emergency – aPTT.
- Rivaroxaban and other “bans”: anti-factor Xa level (normalized for the drug). In an emergency – PT
- Ciraparantag – new magic bullet that binds to all the TSOACs, but it’s not available yet.
- Other treatment options: prothrombin complex concentrates, activated prothrombin complex concentrates, recombinant factor VIIa, plasma, dialysis, transexamic acid.
DILATED IVC – TO DIURESE OR NOT TO DIURESE?
- Does IVC diameter correlate with intravascular volume?
- IVC measured at the junction of the hepatic vein enters the IVC
- IVC compressibility index: IVCmax – IVCmin / IVC min (??)
- False positives (enlarged IVC): pt positioning, mechanically ventilated, large BMIs, males, dialysis patients, tricuspid disease or surgery, tech, young athletes (esp swimmers).
- Some IVC diameters and CVPs:
- IVC diameter < 1.5 = CVP < 5 mmHg
- IVC diameter > 2.0 = CVP > 10 mmHg
- IVC Comp Index <25-50% = CVP > 10
- > 2cm and <40% = CVP > 15% **
- Critical Care 2015; 19:400ff – IVC min was the best predictor of IVF responsiveness in patients.
- Studies have not correlated IVC diameter with clinical outcomes (yet).
- Conclusion: IVC diameter can help in those difficult-to-determine volume situations.
By the way, obesity FALSELY SUPPRESSES BNP.
Morgan Freeman has a falsely high BNP – African-Americans, old age, diabetes mellitus (Freeman has T2DM).
From Rocky Mountain Hospital Medicine conference, 2016, Pell